In the manufacture of semiconductors, material gases containing noxious gas components selected from the group consisting of volatile inorganic hydrides, volatile inorganic halides and organometallic compounds are used. Accordingly, the gases exhausted during the process of semiconductor manufacturing contain unused material gases as residues. Since these material gases, which have toxicity and flammability, are dangerous and harmful components, the harmful components contained in the exhaust gases must be removed before they are released into the atmosphere.
Referring to the treatment of removing such harmful components, the conventional wet treatment method using a scrubber and the like is recently being replaced by the dry treatment method.
For example, Japanese Patent Publication Nos. Hei 3-64166 and Hei 3-64167 disclose methods of removing arsenic by bringing arsenic-containing gases into contact with sorbents containing copper oxides as active ingredients. Japanese Patent Publication No. Hei 4-17082 discloses a method of removing a gaseous silicon compound by bringing a gas containing a gaseous silicon compound into contact with a sorbent containing a copper oxide or a mixture of a copper oxide and a zinc oxide as an active ingredient. Japanese Patent Publication No. Hei 4-57368 discloses a method of removing one or more harmful components contained in a gas, selected from arsine, phosphine, diborane and hydrogen selenide, into contact with a sorbent containing a mixture of a copper oxide and silicon oxide and/or aluminum oxide; and a method of removing a harmful component by bringing a gas containing diborane and/or hydrogen selenide as harmful components into contact with a sorbent containing a mixture of a copper oxide and a zinc oxide as an active ingredient. Japanese Patent Publication No. Hei 4-19886 discloses a method of removing a silane gas by bringing a gas containing a silane gas into contact with a sorbent containing a metal oxide as an active ingredient.
When various kinds of harmful components are to be removed using various types of sorbents as described above, a gas containing a harmful component is generally passed through a column packed with a sorbent so as to bring the harmful component into contact with the sorbent to be removed thereby. In this case, the performance of the sorbent gradually decreases as the treatment of removing the harmful components goes on, and the concentration of the harmful components contained in the gas passed through the sorbent exceeds a predetermined level to cause breakthrough of the sorbent. Accordingly, the sorbent must be renewed or replaced before breakthrough, so that various studies are made with a view to developing detecting agent which can easily and securely detect breakthrough of the sorbent.
Japanese Patent Publication Nos. Hei. 4-79576, 4-79577 and 4-79578 disclose, as detecting agents for detecting gases containing one or more harmful components selected, for example, from arsine, phosphine, diborane, hydrogen selenide, hydrogen sulfide, germane, monosilane, disilane and dicholrosilane, a detecting agent containing a basic copper carbonate as a color forming component, a detecting agent containing a copper salt of an organic acid as a color forming component and a detecting agent containing a mixture of a secondary copper salt and a palladium salt as color forming components, respectively. Japanese Unexamined Patent Publication (Kokai) No. Hei 4-97752 discloses, as a detecting agent for detecting a gas containing one or more harmful components selected from volatile inorganic hydrides such as arsine, phosphine, diborane and hydrogen selenide, a detecting agent containing copper nitrate as a color forming component. Japanese Unexamined Patent Publication (Kokai) Nos. Hei 2-110369 and 2-110370 disclose, as detecting agents for detecting gases containing one or more harmful components selected from carbon monoxide and/or metal carbonyl compounds, or alkyl compound of tin, tellurium cadmium, arsenic, mercury, aluminum, gallium and indium, a detecting agent containing a mixture of a secondary copper salt and a gold salt as a color forming component.
However, these conventional methods of removing harmful components using sorbents containing as active ingredients metal oxides such as copper oxides exhibit poor performances of removing silane. Accordingly, it is necessary to subject the sorbent to grain refining treatment and to increase the specific area thereof by allowing it to be carried on a carrier such as alumina, and besides the manufacture of the sorbent itself is troublesome. Under such circumstances, an advent of a sorbent which can show a higher performance of sorption has been desired. Further, the conventional sorbents require the additional use of a detecting agent for detecting exhaustion of the sorbent.
Meanwhile, the detecting agents described above employ expensive raw materials such as a palladium salt and a gold salt, and costly manufacturing processes including dissolution, precipitation, filtration and drying of the copper salt. The detecting agent containing copper nitrate as the color forming component can exhibit high detection performance, but it is liable to generate NOx if the reaction with the gas of interest goes on excessively.
Therefore, it is a first objective of the invention to provide a method which can exhibit sufficient performance of removing silane series harmful components and which can efficiently remove other harmful components selected from various kinds of volatile inorganic hydrides, various kinds of volatile inorganic halides and various kinds of organometallic compounds. It is a second objective of the invention to provide a detection method using sorbent having a capability of detecting breakthrough of the performance of removing these harmful components.